What is the $y$-intercept of the line $x - 2y = 5$?
Solution: The $y$-intercept is the point at which the line crosses the $y$-axis.  The $x$-coordinate of such a point is 0.  Setting $x=0$ in the equation gives $-2y = 5$, so $y = \boxed{-\frac{5}{2}}$.